Light emitting device and lighting system

ABSTRACT

Disclosed are a light emitting device, a method of fabricating a light emitting device, a light emitting device package, and a lighting system. The light emitting device includes a first conductive semiconductor layer ( 112 ), an In x Ga 1-x N layer (where, 0&lt;x≦1) ( 151 ) on the first conductive semiconductor layer ( 112 ), a GaN layer ( 152 ) on the In x Ga 1-x N layer ( 151 ), a first Al y1 Ga 1-y1 N layer (where, 0&lt;y1≦1) ( 153 ) on the GaN layer ( 152 ), an active layer ( 114 ) on the first Al y1 Ga 1-y1 N layer ( 153 ), and a second conductive semiconductor layer ( 116 ) on the active layer ( 114 ).

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority under 35 U.S.C. §119 to KoreanApplication No. 10-2013-0069782 filed on Jun. 18, 2013, whose entiredisclosure(s) is/are hereby incorporated by reference.

BACKGROUND

1. Field

The embodiment relates to a light emitting device, a method offabricating the light emitting device, a light emitting device package,and a lighting system.

2. Background

A light emitting device includes a P-N junction diode having acharacteristic of converting electrical energy into light energy. Thelight emitting device may include compound semiconductors belonging togroup III and V on the periodic table. The light emitting device canrepresent various colors by adjusting the compositional ratio of thecompound semiconductors.

When forward voltage is applied to the LED, electrons of an N layer arecombined with holes of a P layer, so that energy corresponding to anenergy gap between a conduction band and a valance band may begenerated. The energy is mainly emitted in the form of heat or light. Inthe case of the LED, the energy is generated in the form of light.

For example, a nitride semiconductor represents superior thermalstability and wide bandgap energy so that the nitride semiconductor hasbeen spotlighted in the field of optical devices and high-powerelectronic devices. In particular, blue, green, and UV light emittingdevices employing the nitride semiconductor have already beencommercialized and extensively used.

Recently, as the demand for the high-efficiency LED has been increased,the improvement of luminous intensity has been issued. According to therelated art, as current is increased, a current crowding phenomenonoccurs to lower light output power (Po), which is called “currentcrowding phenomenon”.

Accordingly, the requirements for the improvement in current spreadingand luminous intensity are increased in order to overcome currentcrowding.

In addition, according to the related art, electrons (hot electrons)representing high mobility are not confined in a quantum well, butoverflowed into the P type semiconductor layer, so that light emissionefficiency is lowered.

The above references are incorporated by reference herein whereappropriate for appropriate teachings of additional or alternativedetails, features and/or technical background.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments will be described in detail with reference to thefollowing drawings in which like reference numerals refer to likeelements wherein:

FIG. 1 is a sectional view showing a light emitting device according tothe first embodiment.

FIG. 2 is a view showing an energy band diagram of the light emittingdevice according to the first embodiment.

FIG. 3 is a graph showing electron concentration data of a lightemitting device according to the embodiment.

FIG. 4 is a sectional view showing the light emitting device accordingto the second embodiment.

FIG. 5 is a graph showing an energy band diagram of the light emittingdevice according to the second embodiment.

FIGS. 6 to 7 are sectional views showing the manufacturing process ofthe light emitting device according to the embodiment.

FIG. 8 is a sectional view illustrating a light emitting device packageaccording to the embodiment.

FIG. 9 is an exploded perspective view an example of a lighting systemincluding the light emitting device according to the embodiment.

DETAILED DESCRIPTION

Hereinafter, a light emitting device, a light emitting device package,and a lighting system according to the embodiment will be described withreference to accompanying drawings.

In the description of embodiments, it will be understood that when alayer (or film) is referred to as being ‘on’ another layer or substrate,it can be directly on another layer or substrate, or intervening layersmay also be present. Further, it will be understood that when a layer isreferred to as being ‘under’ another layer, it can be directly underanother layer, and one or more intervening layers may also be present.In addition, it will also be understood that when a layer is referred toas being ‘between’ two layers, it can be the only layer between the twolayers, or one or more intervening layers may also be present.

(Embodiment)

FIG. 1 is a sectional view showing a light emitting device 101 accordingto a first embodiment, and FIG. 2 is a view showing an energy banddiagram of the light emitting device 100 according to the firstembodiment.

The light emitting device 101 according to the embodiment includes afirst conductive semiconductor layer 112, an InxGa1-xN layer (where0<x≦1) 151 on the first conductive semiconductor layer 112, a GaN layer152 on the InxGa1-xN layer 151, a first Aly1Ga1-y1N layer (where 0<y1≦1)153 on the GaN layer 152, an active layer 114 on the first Aly1Ga1-y1Nlayer 153, and a second conductive semiconductor layer 116 on the activelayer 114.

In addition, the embodiment further includes a GaN-based superlatticelayer 124 interposed between the first Aly1Ga1-y1N layer 153 and theactive layer 114. The GaN-based superlattice layer 124 may have abandgap energy level reduced in the direction from the first conductivesemiconductor layer 112 toward the active layer 114.

FIG. 3 is a graph showing electron concentration data of the lightemitting device 100 according to the embodiment.

According to the embodiment, if the light emitting device 100 has thestructure shown in FIG. 2, the light emitting device 100 may have theelectron concentration gradient shown in FIG. 3.

According to the embodiment, a current spreading structure 150 includingthe InxGa1-xN layer 151/GaN layer 152/first Aly1Ga1-y1N layer 153 isprovided under the active layer 114, thereby efficiently spreadingelectrons to overcome an efficiency droop phenomenon in which lightoutput power (Po) is decreased due to the current increase.

For example, according to the embodiment, the tunneling of electrons ispossible due to the structure of the InxGa1-xN layer 151/GaN layer152/first Aly1Ga1-y1N layer 153, so that electrons can be efficientlyspread to overcome the efficiency droop phenomenon.

The concentration of In contained in the InxGa1-xN layer 151 may be inthe range of 2% to 15%. In order to make the meaningful bandgap energydifference between the InxGa1-xN layer 151 and GaN layer 152, theconcentration of In may be 2% or more. In order to prevent electronsfrom being trapped, the concentration of In may not exceed 15%.

As shown in FIG. 2, the GaN-based superlattice layer 124 according tothe embodiment may have the bandgap energy level reduced in thedirection from the first conductive semiconductor layer 112 toward theactive layer 114.

For example, the GaN-based superlattice layer 124 may have the bandgapenergy level reduced in the form of a step in the direction from thefirst conductive semiconductor layer 112 toward the active layer 114,but the embodiment is not limited thereto.

For example, the GaN-based superlattice layer 124 may include afirst-group GaN-based superlattice layer 121 having first bandgap energyat an area A adjacent to the first conductive semiconductor layer 112and a second-group GaN-based superlattice layer 122 having secondbandgap energy lower than the first bandgap energy on the firstconductive semiconductor layer 112 (area B).

In addition, the GaN-based superlattice layer 124 may further include athird-group GaN-based superlattice layer 123 having third bandgapenergy, provided on the second-group GaN-based superlattice layer 122,and provided at an area C adjacent to the active layer 114.

The third bandgap energy may be equal to or lower than the secondbandgap energy, but the embodiment is not limited thereto.

In this case, the first-group GaN-based superlattice layer 121 mayinclude a first-group well 121 w and a first-group barrier 121 b, thesecond-group GaN-based superlattice layer may include a second-groupwell 122 w and a second-group barrier 122 b, and the third-groupGaN-based superlattice layer 123 may include a third-group well 123 wand a third-group barrier 123 b.

The GaN-based superlattice layer 124 may include an InxGa1-xN/GaNsuperlattice layer (where, 0<x≦1), and the difference D between thefirst and second energy bandgap levels may be equal to or higher than aphoton energy level of the GaN-based superlattice layer.

For example, only when the difference (energy difference) of a welldepth in the GaN-based superlattice layer belonging to each group isequal to or higher than the phonon energy (about 88 meV) of InGaN, aportion of the energy of hot electrons may be transferred in the form ofthe phonon energy.

The GaN-based superlattice layer 124 according to the embodiment has atleast two energy steps and the depth of a quantum well (multi-quantumwell) 114 w of the active layer 114 is about 200 meV, so a plurality ofenergy steps can be provided and the number of the energy steps may bedetermined by dividing the depth of the quantum well by the minimumphonon energy.

According to the embodiment, the energy level of each group may beadjusted by adjusting the concentration of In contained in the well ofeach group.

For example, the concentration of In contained in the second-groupGaN-based superlattice layer may be set to a value lower than that of Incontained in the first-group GaN-based superlattice layer 121, therebyreducing the energy level of the second-group well 122 w to lower thanthe energy level of the first-group well 121 w.

According to the embodiment, hot electrons are cooled by the GaN-basedsuperlattice layer having a plurality of energy steps, so that ahigh-power light emitting device having an effective electron injectionlayer can be provided.

According to the embodiment, the thickness of the GaN-based superlatticelayer of each group may be controlled in order to improve the electroninjection efficiency by efficiently cooling the hot electrons.

For example, the thickness of the first-group GaN-based superlatticelayer 121 may be thinner than the thickness of the second-groupGaN-based superlattice layer 122.

In this case, the thickness of the first-group well 121 w of thefirst-group GaN-based superlattice layer 121 may be equal to thethickness of the first-group barrier 121 b of the first-group GaN-basedsuperlattice layer 121 and the first-group well 121 w and the firstgroup barrier 121 b may be prepared with a plurality of cycles. Forexample, the first-group well 121 w and the first-group barrier 121 bmay be controlled to have the same thickness in the range of about 1 nmto 3 nm and may be prepared with a plurality of cycles so that the hotcarriers can be effectively cooled as compared with a case where asingle thick well and a single thick barrier are presented.

In addition, the second-group well 122 w and the second-group barrier122 b of the second-group GaN-based superlattice layer 122 may becontrolled to have the same thickness in the range of about 1 nm to 3 nmand may be prepared with a plurality of periodicities so that the hotcarriers can be effectively cooled as compared with a case where asingle thick well and a single thick barrier are presented.

At this time, the thickness of the second-group well 122 w may be equalto the thickness of the first-group well 121 w and the thickness of thesecond-group barrier 122 b may be equal to the thickness of thefirst-group barrier 121 b. Thus, even if the carriers recognize apredetermined energy barrier in the GaN-based superlattice layer, thecarriers may not be extinguished within the GaN-based superlattice layerdue to the well and the barrier having the regular thickness, so thatthe carriers can be smoothly injected.

According to the embodiment, the total thickness of the second-groupGaN-based superlattice layer 122 may be thicker than the total thicknessof the first-group GaN-based superlattice layer 121. For example, thesecond-group GaN-based superlattice layer 122 may include thesecond-group well 122 w and the second-group barrier 122 b repeatedlyformed with about 8 to 12 cycles and the first-group GaN-basedsuperlattice layer 121 may include the first-group well 121 w and thefirst-group barrier 121 b repeatedly formed with about 3 to 5 cycles.

According to the embodiment, the hot carriers can be stably cooled forlonger time in the second-group GaN-based superlattice layer 122 thatmeets partially-cooled hot carriers rather than the first-groupGaN-based superlattice layer 121 that primarily meets the hot carriers,so the hot carriers may be efficiently cooled without being overflowed.

In addition, according to the embodiment, the thickness of thethird-group well 123 w of the third-group GaN-based superlattice layer123 may be equal to the thickness of the second-group well 122 w andthinner than the thickness of the third-group barrier 123 b.

For example, the thickness of the third-group well 123 w may be in therange of about 1 nm to about 3 nm, and the thickness of the third-groupbarrier 123 b may be in the range of about 7 nm to about 11 nm, but theembodiment is not limited thereto.

According to the embodiment, the third-group barrier 123 b may beadjacent to the active layer 114, and the thickness of the third-groupbarrier 123 b, which is the final barrier, may be thicker than that ofthe barriers and wells of other groups.

According to the embodiment, the third-group barrier 123 b may be dopedwith a first conductive element to improve the electron injectionefficiency

In addition, according to the embodiment, an undoped GaN layer 125 isfurther provided between the third-group barrier 123 b and the quantumwell 114 w of the active layer 114 to prevent the first conductiveelement doped in the third-group barrier 123 b from diffusing into theactive layer 114 and blocking the recombination for light emission.

According to the embodiment, the hot electrons are cooled by theGaN-based superlattice layer having a plurality of energy steps, so thatthe high-power light emitting device having the effective electroninjection layer can be provided.

According to the embodiment, the light emitting device capable ofimproving luminous intensity by improving current spreading, a method offabricating the light emitting device, the light emitting devicepackage, and the lighting system can be provided.

In addition, according to the embodiment, the light emitting devicecapable of improving light emission efficiency by confining electronsinto the active layer, the method of fabricating the light emittingdevice, the light emitting device package, and the lighting system canbe provided.

FIG. 4 is a sectional view showing a light emitting device 102 accordingto a second embodiment, and FIG. 5 is a graph showing an energy banddiagram of the light emitting device 102 according to the secondembodiment.

The light emitting device 102 according to the second embodiment mayemploy the technical features of that of the first embodiment.

According to the second embodiment, differently from the firstembodiment, the GaN-based superlattice layer 124 may not be provided.

In addition, the light emitting device 102 according to the secondembodiment may further include a second Aly2Ga1-y2N layer (where,0<y2≦1) 154 between the first Aly1Ga1-y1N layer (where 0<y1≦1) 153 andthe active layer 114.

The bandgap energy of the second Aly2Ga1 -y2N layer 154 may be higherthan the bandgap energy of the first Aly1Ga1-y1N layer 153.

Accordingly, the tunneling effect of electrodes is increased to enhancecurrent spreading, thereby overcoming the efficiency droop phenomenon.

In addition, according to the second embodiment, a second-concentrationfirst conductive semiconductor layer 113 having a second concentrationhigher than the concentration of the first conductive semiconductorlayer 112 may be further provided between the first conductivesemiconductor layer 112 and the InxGa1-xN layer 151.

The bandgap energy of the second-concentration first conductivesemiconductor layer 113 may be heavier than that of the InxGa1-xN layer151.

According to the embodiment, the second-concentration first conductivesemiconductor layer 113 is provided to increase carrier injectionefficiency, and current is spread in a light emitting device chipthrough the current spreading structure 150 in which heavily-dopedelectrodes spread current, thereby effectively overcoming the efficiencydroop phenomenon.

Hereinafter, the method of fabricating the light emitting deviceaccording to the embodiment will be described with reference to FIGS. 6and 7. Even if the method of fabricating the light emitting deviceaccording to the first embodiment will be described with reference toFIGS. 6 and 7, the embodiment is not limited thereto.

Meanwhile, although FIG. 6 shows a lateral-type light emitting device inthat the light emitting device 101 according to the embodiment is grownon a predetermined growth substrate 105, the embodiment is not limitedthereto. The embodiment is applicable to a vertical-type light emittingdevice in which an electrode is formed on the first conductivesemiconductor layer exposed to the outside after the growth substratehas been removed.

First, in the light emitting device according to the embodiment as shownin FIG. 6, the substrate 105 may include a material representingsuperior thermal conductivity. The substrate 105 may include aconductive substrate or an insulating substrate. For example, thesubstrate 105 may include at least one of sapphire (Al2O3), SiC, Si,GaAs, GaN, ZnO, GaP, InP, Ge, and Ga2O3.

According to the embodiment, a light reflective pattern is provided toincrease light extraction efficiency. For example, the substrate 105 mayinclude a patterned sapphire substrate (PSS) to increase the lightextraction efficiency.

In addition, according to the embodiment, a buffer layer 107 and anundoped semiconductor layer (not shown) are formed on the substrate 105to attenuate the lattice mismatch between a material of the lightemitting structure 110 and a material of the substrate 105. For example,the buffer layer 107 may be formed of group III-V compoundsemiconductors. In detail, the buffer layer 107 may include at least oneof GaN, InN, AlN, InGaN, AlGaN, InAlGaN, and AlInN, but the embodimentis not limited thereto.

Then, a first conductive semiconductor layer 112 is formed on theundoped semiconductor layer. For example, the first conductivesemiconductor layer 112 may include a semiconductor material having acompositional formula of InxAlyGa1-x-yN (0≦x≦1, 0≦y≦1, and 0≦x+y≦1). Indetail, the first conductive semiconductor layer 112 may include atleast one of GaN, InN, AlN, InGaN, AlGaN, InAlGaN, AlInN, AlGaAs,InGaAs, AlInGaAs, GaP, AlGaP, InGaP, AlInGaP, and InP, but theembodiment is not limited thereto.

Next, the current spreading structure 150 including the InxGa1-xN layer151/GaN layer 152/first Aly1Ga1-y1N layer 153 is provided on the firstconductive semiconductor layer 112, thereby efficiently spreadingelectrons to overcome an efficiency droop phenomenon in which lightoutput power (Po) is decreased due to the current increase.

For example, according to the embodiment, the tunneling of electrons ispossible due to the structure of the InxGa1-xN layer 151/GaN layer152/first Aly1Ga1-y1N layer 153, so that electrons can be efficientlyspread to overcome the efficiency droop phenomenon.

According to the embodiment, the bandgap energy of the GaN layer 152 maybe higher than the bandgap energy of the InxGa1-xN layer 151.

The bandgap energy of the GaN layer 152 may be lower than the bandgapenergy of the first Aly1Ga1-y1N layer 153.

In addition, the bandgap energy of the InxGa1-xN layer 151 may be higherthan that of the quantum well 114 w in the active layer 114.

Further, the bandgap energy of the first Aly1Ga1-y1N layer 153 may behigher than that of a quantum barrier 114 b in the active layer 114.

According to the embodiment, any one of the energy bandgap structures isprovided, so that the tunneling of electrons is possible, therebyovercoming the efficiency droop phenomenon.

The concentration of In contained in the InxGa1-xN layer 151 may be inthe range of 2% to 15%. In order to make the meaningful bandgap energydifference between the InxGa1-xN layer 151 and GaN layer 152, theconcentration of In may be 2% or more. In order to prevent electronsfrom being trapped, the concentration of In may not exceed 15%.

The GaN-based superlattice layer 124 may be formed on the currentspreading structure 150, and the GaN-based superlattice layer 124 mayhave a bandgap energy level reduced in the direction from the firstconductive semiconductor layer 112 toward the active layer 114.

For example, according to the embodiment, the GaN-based superlatticelayer 124 may include the first-group GaN-based superlattice layer 121having the first bandgap energy and the second-group GaN-basedsuperlattice layer 122 having the second bandgap energy lower than thefirst bandgap energy and provided on the first-group GaN-basedsuperlattice layer 121.

In addition, the GaN-based superlattice layer 124 may further includethe third-group GaN-based superlattice layer 123 having the thirdbandgap energy and provided on the second-group GaN-based superlatticelayer 122.

In this case, the first-group GaN-based superlattice layer 121 mayinclude the first-group well 121 w and the first-group barrier 121 b,the second-group GaN-based superlattice layer may include thesecond-group well 122 w and the second-group barrier 122 b, and thethird-group GaN-based superlattice layer 123 may include the third-groupwell 123 w and the third-group barrier 123 b.

The GaN-based superlattice layer 124 may include the InxGa1-xN/GaNsuperlattice layer (where, 0<x<1), and the difference D between thefirst and second energy bandgap levels may be equal to or higher than aphoton energy level of the GaN-based superlattice layer.

According to the embodiment, the growth temperature of the first-groupwell 121 w of the first-group GaN-based superlattice layer 121 may behigher than the growth temperature of the second-group well 122 w of thesecond-group GaN-based superlattice layer 122. For instance, thefirst-group well 121 w may be grown at the temperature of about 500 orbelow and the second-group well 122 w may be grown at the temperature ofabout 900 or above.

The GaN-based superlattice layer 124 may be grown at the temperature ofabout 800 or above.

According to the embodiment, the amount of indium (In) in the well inthe GaN-based superlattice layer 124 of each group may be controlledthrough PL (photo luminescence) sub-peak position, but the embodiment isnot limited thereto.

According to the embodiment, the energy level of each group can becontrolled by controlling concentration of indium in the well of eachgroup. For example, the concentration of indium in the second-groupGaN-based superlattice layer 122 is set higher than a concentration ofindium in the first-group GaN-based superlattice layer 121. In thiscase, the energy level of the second-group well 122 w may be lower thanthe energy level of the first-group well 121 w.

According to the embodiment, hot electrons are cooled by the GaN-basedsuperlattice layer having a plurality of energy steps, so that ahigh-power light emitting device having an effective electron injectionlayer can be provided.

In addition, according to the embodiment, the thickness of the GaN-basedsuperlattice layer of each group may be controlled in order to improvethe electron injection efficiency by more efficiently cooling the hotelectrons.

For example, the thickness of the first-group GaN-based superlatticelayer 121 may be thinner than the thickness of the second-groupGaN-based superlattice layer 122.

At this time, the thickness of the first-group well 121 w of thefirst-group GaN-based superlattice layer 121 may be equal to thethickness of the first-group barrier 121 b of the first-group GaN-basedsuperlattice layer 121 and the first-group well 121 w and thefirst-group barrier 121 b may be prepared with a plurality of cycles.For example, the first-group well 121 w and the first-group barrier 121b may be controlled to have the same thickness in the range of about 1nm to 3 nm and may be prepared with a plurality of cycles so that thehot carrier can be efficiently cooled as compared with a case where asingle thick well and a single thick barrier are presented.

In addition, the second-group well 122 w and the second-group barrier122 b of the second-group GaN-based superlattice layer 122 may becontrolled to have the same thickness in the range of about 1 nm to 3 nmand may be prepared with a plurality of cycles so that the hot carriercan be efficiently cooled as compared with a case where a single thickwell and a single thick barrier are presented.

In this case, the thickness of the second-group well 122 w may be equalto the thickness of the first-group well 121 w and the thickness of thesecond-group barrier 122 b may be equal to the thickness of thefirst-group barrier 121 b. Thus, even if the carriers recognize apredetermined energy barrier in the GaN-based superlattice layer, thecarriers may not be extinguished within the GaN-based superlattice layerdue to the well and the barrier having the regular thickness, so thatthe carriers can be smoothly injected.

According to the embodiment, the total thickness of the second-groupGaN-based superlattice layer 122 may be thicker than the total thicknessof the first-group GaN-based superlattice layer 121.

According to the embodiment, the hot carriers can be stably cooled forlonger time in the second-group GaN-based superlattice layer 122 thatmeets partially-cooled hot carriers rather than the first-groupGaN-based superlattice layer 121 that primarily meets the hot carriers,so the hot carriers may be efficiently cooled without being overflowed.

In addition, according to the embodiment, the thickness of thethird-group well 123 w of the third-group GaN-based superlattice layer123 may be equal to the thickness of the second-group well 122 w andthinner than the thickness of the third-group barrier 123 b.

According to the embodiment, the third-group barrier 123 b may beadjacent to the active layer 114, and the thickness of the third-groupbarrier 123 b, which is the final barrier, may be thicker than that ofthe barriers and wells of other groups.

According to the embodiment, the third-group barrier 123 b is doped witha first conductive element to improve the electron injection efficiency.According to the embodiment, the third-group barrier 123 b may beheavily doped with Si so that the electron injection efficiency can beimproved. For example, the third-group barrier 123 b may be doped with19 cc or more of Si, but the embodiment is not limited thereto.

In addition, according to the embodiment, the undoped GaN layer 125 isfurther provided between the third-group barrier 123 b and the quantumwell 114 w of the active layer 114 to prevent the first conductiveelement doped in the third-group barrier 123 b from diffusing into theactive layer 114 and blocking the recombination for light emission.

According to the embodiment, the hot electrons are cooled by theGaN-based superlattice layer having a plurality of energy steps, so thatthe high-power light emitting device having the effective electroninjection layer can be provided.

Then, the active layer 114 is formed on the undoped GaN layer 125.

According to the embodiment, the active layer 114 may include at leastone of a single quantum well structure, a multi quantum well (MQW)structure, a quantum wire structure, and a quantum dot structure.

For example, the active layer 114 may have the MQW structure formed byinjecting TMGa gas, NH3 gas, N2 gas, and trimethyl indium (TMIn) gas,but the embodiment is not limited thereto.

The well layer 114 w/barrier layer 114 b of the active layer 114 mayinclude at least one of InGaN/GaN, InGaN/InGaN, GaN/AlGaN, InAlGaN/GaN,GaAs (InGaAs)/AlGaAs, and GaP (InGaP)/AlGaP pair structures, but theembodiment is not limited thereto. The well layer may be formed ofmaterial having a bandgap lower than a bandgap of the barrier layer.

The barrier layer 114 b may be grown under the conditions of thepressure of about 150 torr to about 250 torr and the temperature ofabout 750° C. to 800° C., but the embodiment is not limited thereto.

Then, according to the embodiment, a second conductive GaN-based layer129 is formed on the active layer 114.

According to the embodiment, the second conductive GaN-based layer 129performs an electron blocking function and an MQW cladding function ofthe active layer 114, so that the light emission efficiency can beimproved. For example, the second conductive GaN-based layer 129 mayinclude a semiconductor based on AlxInyGa(1-x-y)N(0≦x≦1, 0≦y≦1), and mayhave the energy bandgap higher than the energy bandgap of the activelayer 114. The second conductive GaN-based layer 129 may have thethickness of about 100 Å to about 600 Å, but the embodiment is notlimited thereto.

In addition, the second conductive GaN-based layer 129 may include anAlzGa(1-z)N/GaN (0≦z≦1) superlattice layer, but the embodiment is notlimited thereto.

P type ions are implanted into the second conductive GaN-based layer 129to efficiently block overflowed electrons and enhance injectionefficiency of holes. For example, Mg ions are implanted into the secondconductive GaN-based layer 129 at the concentration in the range ofabout 1018/cm3 to about 1020/cm3 to efficiently block overflowedelectrons and enhance injection efficiency of holes.

Next, the second conductive semiconductor layer 116 is formed on thesecond conductive GaN-based layer 129.

The second conductive semiconductor layer 116 may include asemiconductor compound. The second conductive semiconductor layer 116may be realized by using groups III-V-II-VI compound semiconductors, andmay be doped with second conductive type dopants.

For example, the second conductive semiconductor layer 116 may include asemiconductor material having a compositional formula of InxAlyGa1-x-yN(0≦x≦1, 0≦y≦1, and 0≦x+y≦1). If the second conductive semiconductorlayer 116 is a P type semiconductor layer, the second conductive dopant,which serves as a P type dopant, may include Mg, Zn, Ca, Sr, or Ba.

Thereafter, the second conductive semiconductor layer 116 may beprovided thereon with a transmissive electrode 130. The transmissiveelectrode 130 may include a transmissive ohmic layer, and may be formedby laminating single metal, or by laminating a metal alloy and metaloxide in a multi-layer such that carrier injection may be efficientlyperformed.

The transmissive electrode 130 may include at least one of ITO (indiumtin oxide), IZO (indium zinc oxide), IZTO (indium zinc tin oxide), IAZO(indium aluminum zinc oxide), IGZO (indium gallium zinc oxide), IGTO(indium gallium tin oxide), AZO (aluminum zinc oxide), ATO (antimony tinoxide), GZO (gallium zinc oxide), IZON (IZO Nitride), AGZO (Al—Ga ZnO),IGZO(In—Ga ZnO), ZnO, IrOx, RuOx, and NiO, but the embodiment is notlimited thereto.

According to the embodiment, the first conductive semiconductor layer112 may include an N type semiconductor layer and the second conductivesemiconductor layer 116 may include a P type semiconductor layer, butthe embodiment is not limited thereto. In addition, a semiconductorlayer, such as an N type semiconductor layer (not illustrated) havingpolarity opposite to that of the second conductive semiconductor layer116, may be formed on the second conductive semiconductor layer 116.Thus, the light emitting structure 110 may include one of an N-Pjunction structure, a P-N junction structure, an N-P-N junctionstructure, and a P-N-P junction structure.

Subsequently, as shown in FIG. 7, portions of the transmissive electrode130, the second conductive semiconductor layer 116, the secondconductive GaN-based layer 129, the active layer 114, and the GaN-basedsuperlattice layer 124 may be removed to expose the first conductivesemiconductor layer 112 to the outside.

Then, a second electrode 132 is formed on the transmissive electrode130, and a first electrode 131 is formed on the first conductivesemiconductor layer 112 that is exposed.

According to the embodiment, the light emitting device capable ofimproving luminous intensity by improving current spreading, a method offabricating the light emitting device, the light emitting devicepackage, and the lighting system can be provided.

In addition, according to the embodiment, the light emitting devicecapable of improving light emission efficiency by confining electronsinto the active layer, the method of fabricating the light emittingdevice, the light emitting device package, and the lighting system canbe provided.

FIG. 8 is a sectional view illustrating a light emitting device package200 according to the embodiment.

The light emitting device package 200 according to the embodimentincludes a package body 205, third and fourth electrode layers 213 and214 formed on the package body 205, the light emitting device 100provided on the package body 205 and electrically connected to the thirdand fourth electrode layers 213 and 214, and a molding member 240 thatsurrounds the light emitting device 100.

The package body 205 may include silicon, synthetic resin or metallicmaterial. An inclined surface may be formed around the light emittingdevice 100.

The third and fourth electrode layers 213 and 214 may be areelectrically isolated from each other to supply power to the lightemitting device 100. In addition, the third and fourth electrode layers213 and 214 reflect the light emitted from the light emitting device 100to improve the light efficiency and dissipate heat generated from thelight emitting device 100 to the outside.

The lateral type light emitting device shown in FIG. 1 can be employedas the light emitting device 100, but the embodiment is not limitedthereto.

The light emitting device 100 may be installed on the package body 205or the third and fourth electrode layers 213 and 214.

The light emitting device 100 is electrically connected to the thirdelectrode layer 213 and/or the fourth electrode layer 214 through atleast one of a wire bonding scheme, a flip chip bonding scheme and a diebonding scheme. According to the embodiment, the light emitting device100 is electrically connected to the third electrode layer 213 through awire and electrically connected to the fourth electrode layer 214through the die bonding scheme, but the embodiment is not limitedthereto.

The molding member 230 surrounds the light emitting device 100 toprotect the light emitting device 100. In addition, the molding member230 may include phosphors 232 to change the wavelength of the lightemitted from the light emitting device 100.

A plurality of light emitting device packages according to theembodiment may be arrayed on a substrate, and an optical memberincluding a light guide plate, a prism sheet, a diffusion sheet or afluorescent sheet may be provided on the optical path of the lightemitted from the light emitting device package. The light emittingdevice package, the substrate, and the optical member may serve as abacklight unit or a lighting unit. For instance, the lighting system mayinclude a backlight unit, a lighting unit, an indicator, a lamp or astreetlamp.

FIG. 9 is an exploded perspective view an example of a lighting systemincluding the light emitting device according to the embodiment.

As shown in FIG. 9, the lighting system according to the embodiment mayinclude a cover 2100, a light source module 2200, a radiator 2400, apower supply part 2600, an inner case 2700, and a socket 2800. Thelighting system according to the embodiment may further include at leastone of a member 2300 and a holder 2500. The light source module 2200 mayinclude the light emitting device 100 or the light emitting devicemodule 200 according to the embodiment.

For example, the cover 2100 may have a blub shape, a hemisphere shape, apartially-open hollow shape. The cover 2100 may be optically coupledwith the light source module 2200. For example, the cover 2100 maydiffuse, scatter, or excite light provided from the light source module.The cover 2100 may be a type of optical member. The cover 2100 may becoupled with the radiator 2400. The cover 2100 may include a couplingpart which is coupled with the radiator 2400.

The cover 2100 may include an inner surface coated with a milk-whitepaint. The milk-white paint may include a diffusion material to diffuselight. The cover 2100 may have the inner surface of which surfaceroughness is greater than that of the outer surface thereof. The surfaceroughness is provided for the purpose of sufficiently scattering anddiffusing the light from the light source module 2200.

For example, a material of the cover 2100 may include glass, plastic,polypropylene (PP), polyethylene (PE), and polycarbonate (PC). Thepolycarbonate (PC) has the superior light resistance, heat resistanceand strength among the above materials. The cover 2100 may betransparent so that a user may view the light source module 2200 fromthe outside, or opaque. The cover 2100 may be formed through a blowmolding scheme.

The light source module 220 may be disposed at one surface of theradiator 2400. Accordingly, the heat from the light source module 220 istransferred to the radiator 2400. The light source module 2200 mayinclude a light source 2210, a connection plate 2230, and a connector2250.

The member 2300 is disposed at a top surface of the radiator 2400, andincludes guide grooves 2310 into which a plurality of light sources 2210and the connector 2250 are inserted. The guide grooves 2310 correspondto a substrate of the light source 2210 and the connector 2250.

A surface of the member 2300 may be coated with a light reflectivematerial. For example, the surface of the member 2300 may be coated withwhite paint. The member 2300 again reflects light, which is reflected bythe inner surface of the cover 2100 and is returned to the direction ofthe light source module 2200, to the direction of the cover 2100.Accordingly, the light efficiency of the lighting system according tothe embodiment may be improved.

For example, the member 2300 may include an insulating material. Theconnection plate 2230 of the light source module 2200 may include anelectrically conductive material. Accordingly, the radiator 2400 may beelectrically connected to the connection plate 2230. The member 2300 maybe configured by an insulating material, thereby preventing theconnection plate 2230 from being electrically shorted with the radiator2400. The radiator 2400 receives heat from the light source module 2200and the power supply part 2600 and radiates the heat.

The holder 2500 covers a receiving groove 2719 of an insulating part2710 of an inner case 2700. Accordingly, the power supply part 2600received in the insulating part 2710 of the inner case 2700 is closed.The holder 2500 includes a guide protrusion 2510. The guide protrusion2510 has a hole through a protrusion of the power supply part 2600.

The power supply part 2600 processes or converts an electric signalreceived from the outside and provides the processed or convertedelectric signal to the light source module 2200. The power supply part2600 is received in the receiving groove of the inner case 2700, and isclosed inside the inner case 2700 by the holder 2500.

The power supply part 2600 may include a protrusion 2610, a guide part2630, a base 2650, and an extension part 2670.

The guide part 2630 has a shape protruding from one side of the base2650 to the outside. The guide part 2630 may be inserted into the holder2500. A plurality of components may be disposed above one surface of thebase 2650. For example, the components may include a DC converterconverting AC power provided from an external power supply into DCpower, a driving chip controlling driving of the light source module2200, and an electrostatic discharge (ESD) protection device protectingthe light source module 2200, but the embodiment is not limited thereto.

The extension part 2670 has a shape protruding from an opposite side ofthe base 2650 to the outside. The extension part 2670 is inserted intoan inside of the connection part 2750 of the inner case 2700, andreceives an electric signal from the outside. For example, a width ofthe extension part 2670 may be smaller than or equal to a width of theconnection part 2750 of the inner case 2700. First terminals of a “+electric wire” and a “− electric wire” are electrically connected to theextension part 2670 and second terminals of the “+ electric wire” andthe “− electric wire” may be electrically connected to a socket 2800.

The inner case 2700 may include a molding part therein together with thepower supply part 2600. The molding part is prepared by hardeningmolding liquid, and the power supply part 2600 may be fixed inside theinner case 2700 by the molding part.

According to the light emitting device, the method of manufacturing thesame, the light emitting package, and the lighting system of theembodiment, the light extraction efficiency can be increased.

In addition, according to the embodiment, the optical efficiency can beincreased.

The embodiment provides a light emitting device capable of improvingluminous intensity by improving current spreading, a method offabricating the light emitting device, a light emitting device package,and a lighting system.

In addition, the embodiment provides a light emitting device capable ofimproving light emission efficiency by confining electrons into anactive layer, a method of fabricating the light emitting device, a lightemitting device package, and a lighting system.

According to the embodiment, there is provided a light emitting deviceincluding a first conductive semiconductor layer (112), an InxGa1-xNlayer (where, 0≦x≦1) (151) on the first conductive semiconductor layer(112), a GaN layer (152) on the InxGa1-xN layer (151), a firstAly1Ga1-y1N layer (where, 0<y1≦1) (153) on the GaN layer (152), anactive layer (114) on the first Aly1Ga1-y1N layer (153), and a secondconductive semiconductor layer (116) on the active layer (114).

According to the embodiment, there is provided a light emitting deviceincluding a first conductive semiconductor layer (112), an InxGa1-xNlayer (where, 0<x≦1) (151) on the first conductive semiconductor layer(112), a GaN layer (152) on the InxGa1-xN layer (151), a firstAly1Ga1-y1N layer (where, 0<y1≦1) (153) on the GaN layer (152), aGaN-based superlattice layer (124) on the first Aly1Ga1-y1N layer (153),an active layer (114) on the GaN-based superlattice layer (124), and asecond conductive semiconductor layer (116) on the active layer (114).The GaN-based superlattice layer (124) may have a bandgap energy levelreduced in a direction from the first conductive semiconductor layer(112) toward the active layer (114). A difference (D) between first andsecond energy bandgap levels may be equal to or higher than a photonenergy level of the GaN-based superlattice layer (124).

In addition, there is provided a lighting system including a lightingunit including the light emitting device.

The embodiment can provide a light emitting device capable of improvingluminous intensity by improving current spreading, a method offabricating the light emitting device, a light emitting device package,and a lighting system.

The embodiment can a light emitting device capable of increasing lightemission efficiency by confining electrons into an active layer, amethod of fabricating the light emitting device, a light emitting devicepackage, and a lighting system.

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention. Theappearances of such phrases in various places in the specification arenot necessarily all referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with any embodiment, it is submitted that it is within thepurview of one skilled in the art to effect such feature, structure, orcharacteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

What is claimed is:
 1. A light emitting device comprising: a firstconductive semiconductor layer; an In_(x)Ga_(1-x)N layer (where, 0<x≦1)on the first conductive semiconductor layer; a GaN layer on theIn_(x)Ga_(1-x)N layer; a first Al_(y1)Ga_(1-y1)N layer (where, 0<y1≦1)on the GaN layer; an active layer on the first Al_(y1)Ga_(1-y1)N layer;a second conductive semiconductor layer on the active layer; and asecond Al_(y2)Ga_(1-y2)N layer (where 0<y2≦1), interposed betweenbetween the first Al_(y1)Ga_(1-y1)N layer and the active layer, whereinthe second Al_(y2)Ga_(1-y2)N layer has bandgap energy higher thanbandgap energy of the first Al_(y1)Ga_(1-y1)N layer.
 2. The lightemitting device of claim 1, wherein indium contained in theIn_(x)Ga_(1-x)N layer has concentration in a range of 2% to 15%.
 3. Thelight emitting device of claim 1, wherein the GaN layer has bandgapenergy higher than bandgap energy of the In_(x)Ga_(1-x)N layer.
 4. Thelight emitting device of claim 1, wherein the GaN layer has bandgapenergy lower than bandgap energy of the first Al_(y1)Ga_(1-y1)N layer.5. The light emitting device of claim 1, wherein the In_(x)Ga_(1-x)Nlayer has bandgap energy higher than bandgap energy of a quantum well ofthe active layer.
 6. The light emitting device of claim 1, wherein thefirst Al_(y1)Ga_(1-y1)N layer has bandgap energy higher than bandgapenergy of a quantum barrier of the active layer.
 7. The light emittingdevice of claim 1, further comprising a second-concentration firstconductive semiconductor layer interposed between the first conductivesemiconductor layer and the In_(x)Ga_(1-x)N layer.
 8. The light emittingdevice of claim 7, wherein the second-concentration first conductivesemiconductor layer has bandgap energy higher than bandgap energy of theIn_(x)Ga_(1-x)N layer.
 9. The light emitting device of claim 1, furthercomprising a GaN-based superlattice layer interposed between the firstAl_(y1)Ga_(1-y)N layer and the active layer.
 10. The light emittingdevice of claim 9, wherein the GaN-based superlattice layer has abandgap energy level reduced in a direction from the first conductivesemiconductor layer toward the active layer.
 11. The light emittingdevice of claim 10, wherein the GaN-based superlattice layer comprises afirst-group GaN-based superlattice layer having first bandgap energy anda second-group GaN-based superlattice layer provided on the firstconductive semiconductor layer and having second bandgap energy lowerthan the first bandgap energy.
 12. The light emitting device of claim11, wherein a difference between first and second bandgap energy levelsis equal to or higher than a photon energy level of the GaN-basedsuperlattice layer.
 13. The light emitting device of claim 11, whereinthe GaN-based superlattice layer further comprises a third-groupGaN-based superlattice layer provided on the second-group GaN-basedsuperlattice layer and having third bandgap energy.
 14. The lightemitting device of claim 11, wherein the first-group GaN-basedsuperlattice layer has a thickness thinner than a thickness of thesecond-group GaN-based superlattice layer.
 15. A lighting systemcomprising a lighting unit including the light emitting device accordingto claim
 1. 16. A light emitting device comprising: a first conductivesemiconductor layer; an In_(x)Ga_(1-x)N layer (where, 0<x≦1) on thefirst conductive semiconductor layer; a GaN layer on the In_(x)Ga_(1-x)Nlayer; a first Al_(y1)Ga_(1-y1)N layer (where, 0<y1≦1) on the GaN layer;a GaN-based superlattice layer on the first Al_(y1)Ga_(1-y1)N layer,wherein the GaN-based superlattice layer comprises a first-groupGaN-based superlattice layer having first bandgap energy and asecond-group GaN-based superlattice layer provided on the firstconductive semiconductor layer and having second bandgap energy lowerthan the first bandgap energy; an active layer on the GaN-basedsuperlattice layer; and a second conductive semiconductor layer on theactive layer, wherein the GaN-based superlattice layer has a bandgapenergy level reduced in a direction from the first conductivesemiconductor layer toward the active layer, and a difference betweenthe first and second bandgap energy levels is equal to or higher than aphoton energy level of the GaN-based superlattice layer.
 17. The lightemitting device of claim 16, wherein the GaN-based superlattice layerfurther comprises a third-group GaN-based superlattice layer provided onthe second-group GaN-based superlattice layer and having third bandgapenergy.